Die accelerator



Sept. 12, 1967 w. E. MIZE DIE ACCELERATOR 5 Sheets-Sheet 1 Filed Jan. 8, 1965 INVENTOR em. 12, W67 w. E. MIZE DIE ACCELERATIOR 3 Sheets-Sheet 5 Filed Jan. 8, 1965 MIVENTOI? WILL/AM E. M/ZE ig--o- United States Patent 3,340,756 DIE ACCELERATOR William E. Mize, Parma Heights, Ohio, assignor to The Yoder Company, Cleveland, Ohio, a corporation of Ohio Filed Jan. 8, 1965, Ser. No. 424,413 21 Claims. (Cl. 83-320) ABSTRACT OF THE DISCLOSURE This invention relates generally as indicated to a die accelerator and more particularly to an air operated die accelerator for flying cut-offs capable of moving the cutoff to a very high velocity within a short distance.

Automatic flying cut-off machines have been used for many years in steel and non-ferrous rolling mills. Where the work being severed lacks sufiicient stiffness to push the cut-off die or tool forward without buckling, an :accelerator is provided. The accelerator then powers the die table or cut-off tool accelerating the same to the speed of the work whereat the work is cut. After the cut, the die table or tool is then slowed to a stop and returns to its start position.

Accelerators may be of the mechanical type such as illustrated in the copending application of Charles J. Bognar, Serial No. 39,250 entitled, Method and Apparatus for Accelerating a Flying Tool, filed June 28, 1960, now Patent No. 3,169,429, or pneumatic cylinders may be employed to power the cut-off die as disclosed in the copending application of Kenneth R. Keska et al., Serial No. 181,748 entitled, Programmed Cut-Off Mechanism, filed Mar. 22, 1962, now Patent No. 3,173,319. However, most such accelerators for cut-01f machines have one basic limitation and that is the ability to move the cut-off through the cycle in a short distance and still obtain a very high velocity for the relatively heavy die slide and die. Since the mill speed is generally limited by the operational speed of the cut-off, it is apparent that an accelerator capable of obtaining higher velocities in a shorter distance will increase the economic output of the mill.

Such high linear velocities are obtained with the present invention by utilization of an air blast or explosive force obtained from regular plant line air pressures.

It is accordingly a principal object of the present invention to provide an air operated die accelerator capable of moving a die slide and die to a very high velocity within a short distance.

A further principal object of the present invention is the provision of an air operated explosion or blast type accelerator which can accelerate conventional cut-off dies to speeds in excess of 650 feet per minute within a very short distance.

Yet another object is the provision of a die accelerator which can readily be attached to existing cut-01f machines remarkably to improve their performance.

A further object is the provision of a cut-off die accelerator which can readily be adapted to machines employing cut length accuracy improvement devices such as shown in the aforementioned Keska et 'al. copending application while still improving remarkably the speed of operation thereof. V

A yet further object is the provision of a highly simplified air operated accelerator which does not require high pressures from special compressors and the like but need operate only from normal shop line pressures.

Still another object is the provision of such an accelerator having suflicient power for operation of the cutter.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawings:

FIG. 1 is a fragmentary side elevation of an accelerator in accordance with the present invention attached to a conventional cut-off press;

FIG. 2 is a top plan view of the cut-off illustrated in FIG. 1;

FIG. 3 is a fragmentary vertical section of such cut-off as seen from the line 33 of FIG. 1;

FIG. 4 is an enlarged fragmentary longitudinal section of the main actuating cylinder of the accelerator taken substantially on the line 44 of FIG. 2;

FIG. 5 is a fragmentary schematic piping diagram illus trating more clearly the operation of the accelerator;

FIG. 6 is a schematic wiring diagram of the accelerator;

FIG. 7 is a schematic diagram illustrating the position of the various limit switches;

FIG. 8 is a fragmentary top plan view of an accelerator in accordance with the present invention employed with a cam type cut-off; and

FIG. 9 is a fragmentary side elevation of the accelerator and cut-off shown in FIG. 8.

Referring first to FIGS. 1, 2 and 3, there is illustrated a conventional cut-off press to which the accelerator of the present invention is attached. Such cut-off may include a sub-base 1 in which is mounted the motor driven crank shaft and an air operated clutch, electrically controlled, which will provide non-repeat single stroke operation, manual cutting, and jogging. At the rear of the base, there is provided a frame 2 supporting the head 3. The head 3 includes vertically elongated bearing surfaces accurately fitted to machined ways 4 and 5 in the frame 2 and long steel gibs 6 and 7 retain the head in such ways and assure lasting alignment. Vertical movement of the head 3 is obtained by upper and lower connecting rods 9 and 10 seen in FIG. 3 with the lower rod 10 being connected to the crankshaft in the sub-base 1. The upper rod 9 is mounted on bushing 11 on pin 12 mounted in the center rear of the head 3. A screw adjustment 13 is provided between the upper and lower connecting rods 9 and 10 for shut-height adjustment.

Mounted on the underside of the forwardly projecting portion of the head 3 are rails 15 and 16 on which is mounted for sliding movement punch holder 17 downwardly from which project side cams 18 and 19 with the punch or blade 20 therebetween. The sub-base 1 is provided with rails 22 and 23 similar to the rails 15 and 16 provided on the head 3 and mounted on the rails on the base is a die slide 24 on which is supported a die shoe 25, side guides 26 and 27, and upstanding cam guides 28 and 29 which receive the side cams 18 and 19 secured to the punch holder 17. the side guides 26 and 27 are provided with windows indicated at 30 in FIG. 3 through which the elongated work W passes. Mounted for opening and closing movement between the side guides 26 and 27 are die blocks 31 and 32 which may have cooperating work gripping surfaces effective momentarily to surround and grip the elongated work as the blade 20 passes therethrough. Such die blocks are actuated by the side cams 18 and 19 as the blade descends. Reference may be had to the c-opending application of Frank Szel, Serial No. 383,482, entitled Tube Cut-Off Mechanism, filed July 17, 1964, now Patent No. 3,298,213, for an illustration of a sliding cut-off die that may be used in the illustrated cut-off.

It can now be seen that the work W moving in the direction of the arrow 34 passing through the cut-olf dies will be severed as the head 3 descends moving the blade 20 through the work. In order to accelerate or move the cut-off dies with the work to obtain the flying cut-off, there is provided the accelerator mechanism illustrated generally at 35. The accelerator 35 is mounted on a shelf or plate 36 which is supported by vertical plates 37 extending from the sub-base 1 and it will be seen that the accelerator including its support may readily be attached to and removed from the base of the cut-off machine.

The accelerator 35 includes a main actuating cylinder assembly 38 which in reality is a cylinder-valve-cylinder combination. Such cylinder assembly includes an outboard or blast cylinder 39 as seen at the left in FIGS. 4 and which has therein a piston 40, upon which the pressures in the chambers 41 and 42 can exert force. The chamber 41 includes the cavity within cylinder assembly end cap 43 which has a large vertically extending passage 44 extending through the shelf 36 to reservoir 45. It will be appreciated that the area of the piston 40 on the side toward the chamber 42 is less than that on the opposite or chamber 41 side, but the charged pressures in the respective chambers may be such that the piston 40 moves in neither direction. In the illustrated embodiment, the pressures may be equal with friction preventing movement.

On the die or inboard end of the assembly 38 is a cushioning or snubbing cylinder 47 which serves to prevent excessive shock in either direction, and to some extent control the speed of return to the cocked position shown in FIGS. 4 and 5. A piston 48 is mounted within the cylinder 47 and both of the pistons 40 and 48 are mounted on a common piston rod 49. The cylinder 47 extends between cylinder end member 50 and cylinder retainer 51 while the cylinder 39 extends between the end cap 43 and cylinder retainer 52. The cylinder support members 43, 52, 51 and 50 are all mounted on the shelf 36 and the rod 49 extends through the members 52, 51 and 50 and through sliding seals shown at 54 and 55 in the members 51 and 50, respectively.

Between the cylinders 39 and 47 is a blast valve assembly 60 which includes cylinder 61 extending between the retainers 51 and 52 and valve member 62 slidable therein. The valve member 62 is axially slidable within the cylinder 61 and also on the rod 49 and suitable sliding seals are provided between the member and the rod as well as between the member and the cylinder 61, as shown.

The member 62 is provided with a conical valve surface 63 which includes an O-ring seal 64 which cooperates with the tapered or conical seat 65 in the cylinder retainer 52. The valve member 62 is free to move on the rod 49 within the cylinder 61 in response to the pressures in chambers 42 and 66, respectively.

Since it is apparent that the exposed area of the valve member 62 on the chamber 42 side thereof is less than that on the chamber 66 side, equal pressures in such chambers will seat or close the valve moving the same to the left until the seal 64 engages the seat 65. When the valve member 62 is opened or moved to the right as seen in FIG. 4, chamber 42 is exhausted to atmosphere through a multiplicity of holes or ports 68 in the cylinder 61, such ports being located about the circumference of the assembly and which have a combined area approximately equal to that of the valve opening between the seat 65 and the member 62 when the latter is against the 4 retainer 51. In this manner, the entire rod end of cylinder 39 is opened and extremely rapid exhaust of the chamber 42 is obtained. The cylinder 61 may, if desired, be provided with an annular housing, not shown, to channel the exhaust from the ports 68 downwardly through exhaust tube 69 for noise reduction and safety purposes.

The piston rod 49 is secured to the piston 40 at one end by the threaded connection 70 illustrated and at the opposite end is provided with a nut 71 threaded thereon holding in place annular stop 72 which may engage the face member 73 on the cylinder retainer 50 to keep the pistons 48 and 40 from damaging contact with the retainer 51 and the end cap 43, respectively.

The piston rod 49 is not attached to the die slide 24 and it is noted that the stroke of the cylinder-valvecylinder assembly 38 is substantially less than the total horizontal movement of the die slide. For example, in the illustrated embodiment, the stroke of the assembly 38 may be approximately eight inches while the die slide has a stroke from about twenty-four to about thirty inches.

Referring now particularly to FIGS. 2 and 5, it will be seen that on either or both sides of the assembly 38 are conventional piston-cylinder assemblies 75- and 76, the rods 77 and 78 thereof being connected to the die slide 24. These piston-cylinder assemblies have a stroke equal to that of the die slide. Referring now particularly to FIG. 5, it will be seen that air may enter from the regular plant source through shut-off valve 80 and pressure regulator 81 to reservoir 45 and thus the chamber 41 communicating therewith. At the same time, air moves through line 82 through pressure regulator 83 and through deenergized solenoid valve 84 into chamber '66 through line 85. Air pressure thus provided to the chamber 66 causes the valve member 62 to move to the left or to a closed position. Spring loaded check valve 86 requires some pressure before it permits air into the chamber 42. In this manner, the chamber 66 is charged first and shifts the valve 62 to a closed position before the chamber 42 receives a large amount of air. When the valve 62 is closed, the valve 86 then permits a rapid flow of air into the chamber 42 and the aforementioned area differences on each end of the valve 62 maintain the same in a closed condition even though the pressures in chambers 66 and 42 are the same.

At the same time that the chambers 42 and 66 are being charged, air is moving through pressure regulator 88 in the conduit 89 and through deenergized solenoid valve 90 to the rod ends of piston-cylinder assemblies 75 and 76 through respective quick exhaust valves 91. Conduit 92 is connected to the piston-cylinder assembly 75 on the opposite side of the actuator assembly 36. The pressure thus entering the rod ends of the piston-cylinder assemblies 75 and 76 causes the same to retract and cocks the main actuating cylinder assembly 36. The rate of speed at which the die returns and at which cocking occurs is determined by the pressure setting of the pressure regulator 88, as well as by adjustment of the restrictions 93 and 9 4. The restrictions '93, of course, control the flow rate from the blind ends of the piston-cylinder assemblies 75 and 76 and the restriction 94 controls the flow rate from the outboard end of the cushioning or snubbing cylinder 47.

Referring now to FIG. 6, there is illustrated a simple electrical control which may be used with the present invention. Contacts 96 and 97 may be actuated when the material drive or mill is running. Limit switch 98 is the flag limit switch which is mounted on the material run-out table and rotary limit switch 99 may be operated by a cam 100 on the crankshaft so that the contacts open as the cutter or blade leaves the material and recloses as the cut-off head approaches its top or stop position. The switch contacts 98, 99 and 96 are in series with a control relay 101 which when actuated closes contacts 102 and 103 controlling solenoids 104 and 105 actuating valves 84 and 90, respectively. (See FIG. 5.)

Operation With the mill drive running, the material moving in the direction of the arrow 34 strikes a flag 108 on the run-out table 109 as seen in FIG. 7 closing contacts 98 to energize relay 101 which closes contacts 102 and 103 energizing both solenoid valves 84 and 90. When valve 90 shifts, quick exhaust valve 91, which may be mounted right on the cylinder for minimum air travel and rapid exhaust, shifts and exhausts chamber 110 in the piston-cylinder assemblies 75 and 76. The shifting of the valve 84 exhausts chamber 66 which immediately opens valve member 62, which in turn exhausts chamber 42. It is here noted that the check valve 86 prevents the exhausting of chamber 42 until the valve member 62 is open.

The pressure in chamber 41 now moves the piston 40 and the die slide 24 forward at a rate of acceleration determined by the setting of the pressure regulator 81. Atmosphere freely enters the chamber 111 at the blind end of each cylinder 75 and 76 through check valves 112 as well as chamber 113 through check valve 114. It is noted that the chamber 115 on the opposite side of the snubber or cushioning piston 48 is also provided with a check valve 116 and an adjustable restriction 117.

Within the stroke ofthe piston 40 the die slide 24 is accelerated to tube or work speed and the die slide 24 leaves contact with the end of the piston rod 49 and continues forward or to the right as seen in FIGS. 4 and 5. As the piston 48 moves forward, pressure builds up in the chamber 115 due to the restriction 117 and snubs or cushions the forward motion of the rod 49 and the pistons thereon.

The cut cycle may be initiated either by another contact in the flag limit switch 108 or by a limit switch 118 actuated by the passage of the die slide as seen in FIG. 7. It will be appreciated that other means may be provided to energize the cut cycle in response to work end position, die position, the relative speeds of the two, and like factors.

As the cut cycle continues and as the blade or cutter comes back out of the material, the rotary contact 99 will open deenergizing solenoid valves 84 and 90. Quick exhaust valves 91 then reclose and pressure is supplied to chambers 110 in the piston-cylinder assemblies 75 and 76 to brake and stop the die slide. Such pressure within the chambers 110 then returns the die slide and recocks the assembly 36. In this manner, the system is then ready for the next explosion or actuation.

When the processing line or material drive is stopped, the contacts 96 and 97 return to the normal position as shown in FIG. 6 and the latter energizes the solenoid 104 of valve 84 but not the solenoid 105 of valve 90. Then, the pressure in chamber 41 works against that in chamber 110 of each of the piston-cylinder assemblies 75 and 76 and the die slide moves forward to the end of the stroke of the piston rod 49. This tends to move the die toward the center of the machine opening as seen in FIG. 1 for stationary cuts, thereby avoiding excess mechanical stresses in the cut-off head 3 and the support members. When the line is restarted, extremely rapid recocking occurs by the energization of the solenoid 105 through the relay 101. Such recocking occurs in approximately 0.3 second.

It will be appreciated that other control circuits incorporating devices to prevent overtravel, run safe conditions, and the like may be employed. For example, in FIG. 7, there is illustrated the position of a cut and/or die return switch 120 sensing the position of the die slide at its cocked position. Because of the extremely rapid acceleration obtained with the explosive or blast cylinder assembly, in some cases depending upon the work speed, the cut cycle may be initiated as soon as the die slide 24 leaves its cocked position. The speeds obtained by the accelerator can, of course, be varied by adjusting the pressure regulator 81 and, for example, a setting of about 30 p.s.i. will produce an acceleration to about 300 feet per minute in the illustrated embodiment. Since plant line pressures are available to approximately p.s.i., it can be seen that extremely rapid speeds may be obtained. Also, as seen in FIG. 7 an overtravel switch 121 may be positioned near the end of the path of movement of the die slide 24 to detect an overtravel condition. On the run-out table 109, a dump switch 122 may be positioned beyond the flag 108 for the purpose of clearing the cut stock from the path of the oncoming work.

Cut-01f embodiment shown in FIGS. 8 and 9 In this embodiment of the invention, there is illustrated a cut-off machine which is designed to synchronize die speed to work speed of approximately 600 feet per minute, and, for the particular machine illustrated, to cut aluminum, brass, or copper tubing in sizes ranging from /s-inch 0D. to %-inch O.D. As opposed to the FIG. 1 embodiment wherein the air blast accelerator is simply attached to a conventional cut-off press, in this embodiment a single power source may be used for both accelerating the die and operating the cutter. The cut-off unit thus involves two basic assemblies, namely, the power source which is the air blast accelerator and a cut-off mechanism. The air blast accelerator may be substantially that shown in the FIG. 1 embodiment, but need not be controlled or moved to a horizontal center position when the processing line is stopped.

Referring first to FIG. 9, it will be seen that the cutoff may be mounted on a table with the die mechanism illustrated generally at 131 being mounted for limited horizontal sliding movement on two shafts 132 and 133 which extend between frame uprights 134 and 135 mounted on the table or base 130. A top plate 136 extends between such uprights and is provided with a window or opening 137. The tubular workpiece 140 enters the machine from the right as viewed in FIG. 9 and passes into a guide tube 141 mounted in bushing 142 in the upright 135 and secured at 143 to the die assembly 131. The workpiece then passes through a set of guide rollers 144, through the clamping dies and cut-01f mechanism illustrated generally at 145, and then through exit guide rollers 146 into exit guide tube 147. Such exit guide tube is secured at 148 to the die assembly 131 and is mounted in bushing 149 in the exit upright 134. The workpiece then moves on to the left onto a run-out table, not shown.

The cut-olf press or die assembly 131 will move to the left along the guide rods 132 and 133 as the result of the action of the accelerator mechanism shown generally at 150. Such accelerator may be substantially identical to that disclosed in the FIG. 1 embodiment and com prises the actuator assembly 151 which includes reading from right to left the blast cylinder 152, the blast valve 153, and the snubber or cushioning cylinder 154. The rod of the assembly 151 has mounted thereon the blast piston 155 and the cushioning piston 156 and is attached at its inboard end to pusher block 157.

On each side of the assembly 151 there is positioned the die return piston-cylinder assemblies 158 and 159, the rods 160 of which are connected at 161 to the assembly 131. Referring now to the die assembly 145, the cut-off blade 163 is carried by support member 164 which is moved upwardly to perform the cutting operation. Such upward movement is obtained when rollers 165 engage the rise portion 166 of cam tracks 167. The rollers 165 are mounted on arms 168 which are in turn mounted on a transverse shaft 169 which is mounted on block 170 of the assembly 131. At the center of such transverse shaft there is provided an arm having a ball end 172 thereon engaged within a ball socket in the blade carrier 164. The center arm supporting the ball 172 is approximately twice as long as the arms 168 and the ball 172 will therefore move at approximately twice the rotational velocity of the rollers 165. The cam surface 166 on the tracks 167 are such that after acceleration of the blade support 164, the blade 163 will reach a velocity Which is constant and about twice that of the forward motion of the cutting assembly. Accordingly, if the accelerator assembly 150 moves the assembly 131 at about 600 feet per minute, the blade 163 will be moving up wardly at about 1200 feet per minute.

Attached to the blade support 164 through guide rods 174 are springs 175 urging the support 164 and thus the blade 163 downwardly. Such springs then tend to keep the rollers 165 in contact with the cam track 167. The guide rods 174 also serve to eliminate twist in the blade support 164 as well as in the blade. The springs 175 assist in the return of the blade support 164, and also absorb a portion of the energy remaining in the support and blade 163 after the cut has been made.

As the blade support 164 moves upwardly, cams 176 attached there to close die blocks 177 through rollers 178 to confine the tube to be cut. The tube preferably is not clamped by such die blocks, but approximately 0.005 inch clearance is provided. The die blocks 177 may be carried on transversely extending shafts 180 for movement toward and away from a tube confining position.

After the cut, the remaining energy in the moving parts may cause the rollers 165 to leave the cam tracks 167 and move upwardly toward the top track surface 181. Such top track surface may be formed as part of the snubber 182 mounted on the rods, not shown, of snubber piston-cylinder assemblies 183 and 184. Such snubber assemblies will then absorb the remaining energy in the upward vertical movement of the blade and holder and the springs 175 will then return the blade to its lower position and additional blade return force may be developed in the falling portion of the upper cam track 181.

Referring now particularly to FIG. 8, it will be seen that soon after the blade has cut the work and then returned while the cut-off assembly 131 continues in its forward motion, the rollers 165 will cont-act deflecting cam tracks 186 and 187 on pivot members 188 and 189 which contain the cam tracks 167. As such forward motion continues, the members 188 and 189 pivot about the axes 190 and 191, respectively, placing the rollers 165 on a new path 192 which lies behind and slightly lower than the path 167. The path 192, of course, does not have the cam rise 166 therein so that as the cut-off assembly 131 is returned by the piston-cylinder assemblies 158 and 159, the rollers are not cammed and no cut-off motion occurs.

A piston-cylinder assembly 194 seen in FIG. 9 has the rod 195 thereof projecting through the base member 196 may be employed to engage the rollers 165 when the assembly 131 is properly positioned thereover and thus rotate the arms 168 to obtain a stationary or manual cut.

It can now be seen that there is provided in the embodiment of FIGS. 8 and 9 a cut-off machine utilizing the power source of the air blast accelerator for both accelerating the die and operating the cutter. The high speed obtained by moving the die forward by means of the accelerator may then be employed to impart an even higher speed to the movement of the cutter through the work. In this manner, the explosive or air blast accelerator of the present invention may be employed in conventional press type cut-offs remarkably to improve the performance thereof and may also be utilized to impart the necessary cutting action to the blade in addition to accelerating the same to the speed of the work.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I, therefore, particularly point out and distinctly claim as my invention:

1. A cut-off for elongated travelling work comprising a cut-off die mounted for movement with such work, an

accelerator for moving such die to the speed of the work for the operation of the die, said accelerator comprising an air blast cylinder having a piston rod in driving engagement with such die, the stroke of said rod being shorter than the stroke of such die, and an air blast valve at the rod end of said air blast cylinder operative rapidly to exhaust the same where-by said rod will drive such die to the speed of the work.

2. A cut-off as set forth in claim 1 including means to stop said cut-off after the work has been severed and to return the same to starting position while simultaneously recocking said air blast cylinder for operation of the next cut-off cycle.

3. A cut-off as set forth in claim 1 wherein said air blast valve comprises a valve member mounted on said rod for movement therealong operative when moved to open the rod end of said air blast cylinder.

4. A cut-off as set forth in claim 1 including a snubber cylinder in tandem with said air blast cylinder operative to cushion the movement of said rod.

*5. A cut-off as set forth in claim 1 including an air reservoir in communication with the blind end of said air blast cylinder operative to store energy for driving said rod against said cut-off, and means to regulate the pressure of the air within said reservoir to control the ultimate speed of said cut-off.

6. A cut-off as set forth in claim 1 including cam means responsive to movement of said cut-off with such work operative to actuate said cut-off into such work, and means operative to increase the velocity of said cutoff into the work over that of the cut-off with the work.

7. In combination, a flying tool for elongated travelling work, an accelerator operative to move said tool to the speed of the work comprising a rod in driving engagement with said tool, and means explosively to actuate said rod through a stroke shorter than that of said tool to impart to the latter a velocity equal to that of the work.

8. The combination set forth in claim 7 wherein said means explosively to actuate said rod includes a cylinder surrounding said rod, means to store energy within said cylinder, and means to release said energy to obtain such explosive actuation.

9. The combination set forth in claim 8 wherein said cylinder and rod comprise a pneumatic piston-cylinder assembly, an air reservoir having direct communication with the blind end of said assembly, and means quickly completely to exhaust the rod end of said assembly to obtain such explosive actuation.

10. The combination set forth in claim 9 including means to brake said flying tool and return the same to starting position while simultaneously recocking said pneumatic piston-cylinder assembly for the next cycle of operation.

11. The combination set forth in claim 10 including a snubber piston-cylinder assembly in tandem with said pneumatic piston-cylinder assembly operative to cushion the movement of said rod.

12. The combination set forth in claim 11 wherein the means to exhaust quickly and completely the rod end of said pneumatic piston-cylinder assembly comprises an air blast valve interposed between said assembly and said snubber piston-cylinder assembly.

13. The combination set forth in claim 12 wherein said air blast valve is pneumatically operated and effective to open the rod of said pneumatic piston-cylinder assembly to actuate said rod through said stroke.

14. In combination, a flying tool for elongated travelling work, an accelerator for said tool operative to move said tool from a starting at rest position to the speed of the work comprising an air blast piston-cylinder assembly in driving engagement with said tool, means to store energy in said cylinder, and means to release said energy to drive said tool to the speed of the work.

15. The combination set forth in claim 14 including an air reservoir in direct communication with the blind end of said air blast piston-cylinder assembly, and means to regulate the pressure of the air within said reservoir to control the ultimate speed obtained for said flying tool.

16. The combination set forth in claim 14 including means to brake said tool and return the same to starting position while simultaneously recocking said air blast piston-cylinder assembly for operation of the next cycle.

17. The combination set forth in claim 14 including pneumatic piston-cylinder assemblies having a stroke equal to that of the tool operative to brake said tool and return the same to starting position while simultaneously recocking said air blast piston-cylinder assembly for operation of the next cycle.

18. The combination set forth in claim 14 including means responsive to the completion of the operation of the tool on such work to brake such tool and return the same to such starting at rest position while simultaneously storing energy in said cylinder.

19. A die accelerator for a cut-off for elongated travelling work comprising a blast cylinder and a snubber cylinder arranged in tandem and having a common rod in driving engagement with said cut-off, a blast valve interposed between said blast cylinder and snubber cylinder operative rapidly to exhaust said blast cylinder whereby the latter will drive said cut-oif to the speed of the Work, said snubber cylinder cushioning movement of said rod.

20. In combination, a flying tool for elongated travelling work, an accelerator for said tool operative to move said tool to the speed of the work comprising an air blast piston-cylinder assembly in driving engagement with said tool, means to store energy in said cylinder, and means to release said energy to drive said tool to the speed of the work, said means to release said energy comprising a blast valve at the rod end of said air blast piston-cylinder assembly, said blast valve including an annular valve member having a frusto-conical surface adapted to seat -in the rod end of said assembly.

21. In combination, a flying tool for elongated travelling work, an accelerator for said tool operative to move said tool to the speed of the work comprising an air blast piston-cylinder assembly in driving engagement with said tool, means to store energy in said cylinder, and means to release said energy to drive said tool to the speed of the Work, said means to release said energy comprising a pneumatically operated valve member on the piston rod of said air blast cylinder assembly having differential areas on opposite sides thereof operative to maintain the valve member closed when the air pressures thereon are equal.

References Cited UNITED STATES PATENTS 1,185,787 6/1916 Ford 8332O X 1,498,550 6/1924 Johnston 83320 X 1,648,829 11/1927 Sessions 83319 X 2,661,599 12/1953 Folmer 92-151 2,917,305 12/1959 Talbot S3320 X 3,106,134 10/1963 Osborne 91461 X WILLIAM W. DYER, IR., Primary Examiner. JAMES M. MEISTER, Examiner. 

1. A CUT-OFF FOR ELONGATED TRAVELLING WORK COMPRISING A CUT-OFF DIE MOUNTED FOR MOVEMENT WITH SUCH WORK, AN ACCELERATOR FOR MOVING SUCH DIE TO THE SPEED OF THE WORK FOR THE OPERATION OF THE DIE, SAID ACCELERATOR COMPRISING AN AIR BLAST CYLINDER HAVING A PISTON ROD IN DRIVING ENGAGEMENT WITH SUCH DIE, THE STROKE OF SAID ROD BEING SHORTER THAN THE STROKE OF SUCH DIE, AND AN AIR BLAST VALVE AT THE ROD END OF SAID AIR BLAST CYLINDER OPERATIVE RAPIDLY TO EXHAUST THE SAME WHEREBY SAID ROD WILL DRIVE SUCH DIE TO THE SPEED OF THE WORK. 